Microbial population biology covers a diverse range of cutting edge issues in the microbial sciences and beyond. Firmly founded in evolutionary biology and with a strongly integrative approach, the GRC in Microbial Population Biology attracts researchers from evolutionary biology, ecology, computational biology, molecular biology, medical microbiology and epidemiology, bacterial genetics, population genetics, and more recently, systems biology. Research at the cutting edge of this rapidly growing field is consistently innovative (high impact papers in the top journals is the norm). This application seeks funding to support a special session on the evolution of infectious disease at the 2009 meeting of the Microbial Population Biology GRC. The emergence of new kinds of infectious disease (including antibiotic resistance) is a reality. Recent years have seen the emergence of HIV, SARS and the world remains acutely aware of the possibility of a new influenza pandemic. While the study of diseases typically falls within the domain of clinicians and microbiologists, the emergence of new infectious disease is primarily a problem in evolution and ecology. Molecular biology might tell us how many mutations are needed to switch from H5N1 (bird flu) to a form that is transmissible through human populations, but it is evolutionary biology that asks about the origin of these mutations, the order in which they need to occur and the likelihood of their occurrence: from this it becomes possible to build models and make predictions. Real progress in understanding the emergence of infectious disease and antibiotic resistance (including its control) requires that physicians talk with evolutionary biologists;that theorists talk with experimentalists. We propose to bring together a diverse spectrum of scientists in order to focus on cutting edge issues. The ensuing exchange of ideas - particularly when fuelled by open debate among the full spectrum of meeting participants - will provoke the emergence of new concepts and approaches for the study of the emergence of infectious disease that will ultimately make a difference to what is arguably the most significant public health issue of our time.